1. Field of the Invention.
This invention relates generally to separating processes wherein a liquid based mixture may be divided into distinct phases to allow selective processing of each such phase. More particularly, this invention relates to treating oil which has become contaminated during use in an industrial process. By being able to remove the contaminants from the oil, the oil may be returned to the industrial process for reuse.
2. Prior Art
Separating processes applicable to liquids as well known and may be divided into three general categories. A first category includes mechanical means in which physical properties are considered. For example, a filter media may be used to retain solid particulate in the liquid as it flows through the filter media.
Where the particle size of the particulate is generally submicronic, mechanical filtration is impractical because an extremely tight filter septum is required to effect separation. Such a septum rapidly blinds off, resulting in short filter cycles and high media usage.
Another means of separation is by settling. However, where the particulate size is small and the difference in specific gravity of the liquid and particulate is not substantial, the particulate tends to stay in suspension. Under these conditions, separation may take days. Centrifugal separation can also be used but extremely high rotational speed can be required.
Other separating methods include magnetic separators, electromagnetic devices, electrophoresis, electrostriction and electrostatic separation. All of these means are expensive and produce questionable results.
Another such process relying on physical properties for separation is disclosed in U.S. Pat. No. 3,637,490. This reference suggests that waste solids may be separated from industrial or municipal waste water by allowing microballoon like objects made of a film forming agent to float upwardly through the waste water. The waste solids adhere to the surface of the objects and accumulate on a top surface of the waste water to form a scum which may be readily removed.
A second general category of liquid separating processes are ones in which chemical properties are considered. One such example is disclosed in U.S. Pat. No. 2,980,608 wherein a flocculating agent is added to waste water to improve the separation of suspended solids in the waste water.
Another example of chemical separation is disclosed in U.S. Pat. No. 1,727,165 wherein an oil-water emulsion is treated with a surface tension depressant such as an oil soluble mineral oil-sulphuric acid salt to cause the water and oil to separate into distinct phases.
A third general category of separating processes relies on both physical and chemical properties to achieve its intended purpose.